Telescoped caseless ammunition having a gas barrier within the propellant charge

ABSTRACT

A propellant charge for a telescoped round of caseless ammunition is provided with a gas barrier which separates the propellant charge into a forward-end and an aft-end. The gas barrier temporarily delays ignition of the forward-end of the propellent charge resulting in improved ballistic performance for the caseless round.

United tates Patent inventor John A. Ruth Westerloo, Del.

Appl No. 861,886

Filed Sept. 29, 1969 Patented Dec. 14, 197i Assignee Hercules Incorporated Wilmington, Del.

TELESCOPED CASELESS AMMUNITION HAVING A GAS BARRIER WITHIN THE PROPELLANT CHARGE ll Claims, 3 Drawing Figs.

U.S. Cl 102/40, l02/DIG. 1

Int. Cl F42b 5/18 [50] Field oi Search 102/38, DIG i, 43, 40

[56] References Cited UNlTED STATES PATENTS 3,482,516 12/1969 Farmer etai. i02/DlG. 1

Primary Examiner- Robert F Stahl Attorney-Michael B. Keehan ABSTRACT: A propellant charge for a telescoped round o caseless ammunition is provided with a gas barrier which separates the propellant charge into a forward-end and an aftend. The gas barrier temporarily delays.v ignition of the forward-end of the propellent charge resulting in improved ballistic performance for the caseiess round.

Patented Dec. 14, 1971 3,62%,51

FIG.3

JOHN A. RUTH INVENTOR ATTORNEY TELESCOPED CASELESS AMMUNITION HAVING A GAS BARRIER WITHIN THE PROPELLANT CHARGE This invention relates to the method of improving the ballistic performance of telescoped caseless ammunition through use of a gas barrier. More particularly, this invention relates to an improved propellant charge for telescoped caseless ammunition in which the propellant charge is separated by a gas barrier into a forward-end and an aft-end.

Telescoped caseless ammunition is comprised of a propellant charge having an axial bore or cavity, a projectile housed entirely within the axial bore of the propellant charge and a primer positioned aft of the projectile. Various embodiments of telescoped caseless ammunition are disclosed in U.S. Pat. application, Ser. No. 694,310; now U.S. Pat. No. 3,482,516 filed Dec. 28, 1967 by L. 1. Farmer et al. and entitled "Caseless Cartridges Having the Projectile Housed in the'Propellant Charge."

When a telescoped round of caseless ammunition is loaded into the chamber of a gun, the projectile. being housed in the propellant charge, is not seated in the barrel of the gun as is the projectile of a round of conventional ammunition when in a gun chamber. Upon initiation of the primer of the telescoped round, the projectile is forced forward into the barrel of the gun and becomes seated in the barrel. During the time interval from initiation of the primer until the projectile is seated in the barrel of the gun, some of the gases of combustion from the primer and from the initiated propellant charge can escape through the barrel ahead of the projectile resulting in a loss of impetus. Early work in the development of telescoped caseless ammunition indicated only negligible loss of propulsive gas from telescoped caseless ammunition. However, later work has shown loss of gas ahead of the projectile to be adversely affecting the ballistics of the telescoped rounds. It has now been found that by delaying the ignition of the forward-end of the propellant charge of a telescoped round that improved ballistic efficiency of the round is obtained.

Propellant charges for telescoped caseless ammunition are prepared by molding granules of smokeless powder, so that the individual propellant granules retain their identity in the charge. Propellant charges for caseless ammunition are porous, i.e., they have a series of interstitial passages throughout the charge. While not being bound by any theory, it is believed that ignition of the propellant charge proceeds by the adiabatic compression of hot gases within the porous charge following initiation of the ignition charge by a primer. By temporarily restraining the flow of hot gases and/or flame through the propellant charge through use of a gas barrier, it is possible to momentarily delay ignition of the forward end of the propellant charge. It is theorized that the momentary delay in the ignition of the forward-end of the propellant charge allows the projectile of the telescoped round to move into the barrel of the firearm prior to ignition of the forward-end of the propellant charge. Thus, the potential loss of propulsive gas is reduced and improved ballistic performance results. The time interval during which the gas barrier performs its function is on the order of l to milliseconds.

The gas barrier of this invention comprises a material which will momentarily restrict flow of hot gases through the interstitial passages in the porous propellant charge. The gas barrier in its simplest form comprises a wafer which separates the propellant charge into a forward-end and an aft-end said gas barrier having at least the same cross section as the cross section through the aft-surface of the forward-end of the propellant charge. The gas barrier of this invention can either be prepared from a normally solid material such as styrofoam, or from a liquid material which will cure to a solid and which is nonporous. The gas barrier can also be extended to cover any exposed surface area of the forward-end of the propellant charge for the purpose of momentarily delaying flow of hot gas through the forward-end of the charge, thereby delaying the ignition thereof.

The position of the gas barrier in the propellant charge is important in order to obtain substantial improvement in ballistic performance of telescoped caseless ammunition. It is generally preferred to design the propellant charge so that the forward surface of the gas barrier in the assembled charge is in line with or aft of contacting surface of the projectile housed within the propellant charge. The contacting surface of the projectile is defined as the surface of the projectile that initially contacts the rifling in the barrel'of the gun in which the telescoped round is tired. Thus, when the projectile housed within a telescoped round of caseless ammunition has a rotating band, the contacting surface of the projectile is the forward-surface of the rotating band. When the projectile employed has a guilding metal coating, the contacting surface is the base of the ogive of the projectile.

For a more complete understanding of this invention reference is made to the following drawings.

FIG. I is a longitudinal view partly in section illustrating a gas barrier prepared from a solid material separating the propellant charge into a forward-end and an aft-end.

FIG. 2 is a view taken along line 2-2 of FIG. 1 illustrating the shape of the gas barrier covering the cross-sectional area of the forward-end of the propellant charge.

FIG. 3 is a longitudinal view partly in section illustrating gas barrier separating the propellant charge into a forward-end and an aft-end and covering the cross-sectional area of the aftsurface of the forward-end of the propellant charge as well as the outside surface of the forward-end of the propellant charge and a portion of the surface defined by the axial cavity in the forward-end of the propellant charge.

In FIG. 1 a telescoped round of caseless ammunition is shown comprised of a propellant charge having an aft-end 10, a forward-end 12, a gas barrier 14, a primer 16, and a projectile 18. The gas barrier 14 separates the aft-end l0 and the forward-end 12 of the propellant charge. The forward-surface 20 of the aft-end 10 of the propellant charge and the aft-surface 22 of forward-end 12 of the propellant charge are adhesively secured to gas barrier 14. The gas barrier 14 has the same cross-sectional area as the cross-sectional area provided by the forward-surface 20 of the aft-segment 10 of the propellant charge, and has at least the same surface area as the aft-surface 22 of the forward-end 12 of the propellant charge. Projectile 18 has a rotating band 24 having a contacting surface 25 and an aft-surface 26. The aft-surface 26 of rotating band 24 rests on gas barrier 14. The outside diameter of the rotating band 24 is only slightly smaller in diameter than the inside diameter of the forward-end 12 of the propellant charge allowing the projectile to be slidably moved into position within the propellant charge. Primer 16 is housed within propellant plug 28. When primer 16 is initiated by impact with a firing pin (not shown) the primer generates hot gases which force projectile l8 forward. Gas barrier 14 momentarily delays ignition of the forward-end 12 of the propellant charge. Projectile 18 moves into the barrel of the weapon prior to complete ignition of the forward-end of the propellant charge. The shape of gas barrier 14 is clearly illustrated in FIG. 2.

In FIG. 3 a round of telescoped caseless ammunition is shown in which the gas barrier is a cured resin. The gas barrier 30 separates the propellant charge into a forward-end 32 and an aft-end 34. The projectile 36 housed within the propellant charge has a guilding metal jacket. The base 38 of the ogive 40 of the projectile 36 defines the contacting surface of the projectile 36. The forward surface 42 of gas barrier 30 is in line with the contacting surface of the projectile 36. The outside surface 44 and about half of the inside surface 46 of the forward-end 32 of the propellant charge are coated with a cured resin which comprises additional gas barrier. A primer 48 and an auxiliary ignition charge 50 are secured in a propellant plug 50 in the aft-end 34 of the propellant charge.

It is important when employing a curable resin as a gas barrier in a propellant charge not to coat any of the aft-end of the propellant charge with the resin since it is necessary for proper functioning of the round that the aft-end of propellant charge ignite immediately following initiation of the primer to aid in forcing the projectile into the barrel of the gun.

The following examples will more fully illustrate this invention. All parts and percentages are by weight unless otherwise specified.

The propellant charges in the examples that follow are prepared by compression molding of granules of smokeless powder. Smokeless powder granules are charged to a mold of the desired configuration and covered with a mixture of solvents for the propellant granules to soften the surfaces thereof thereby aiding in consolidation of the charge during molding. The solvent is driven from the mold during compression of the charge. Example 1 is a control round and represents results from firing of a telescoped round without a gas barrier. Example 2 is a control round in which a gas barrier as described in FIG. 1 is employed. ln this control round the projectile is I seated in the barrel of the gun prior to firing (nontelescoped).

Examples 3-6 illustrate firing of telescoped rounds with a gas barrier prepared in the form of a wafer as shown in FIG. 2. The gas barrier is prepared from M-B sheet propellant as defined in MlL-STD-652B, dated Feb. 13, 1969. The wafer of sheet propellant conforms to the cross-sectional surface of the aft-segment of the propellant charge and covers the total cross-sectional area provided by the aft-surface of the forward-end of the propellant charge. Five thin washers of M8 of propellant having a thickness of about 0.005 in. each are bonded together by softening the surfaces with acetone and pressing the washers together to form the gas barrier. The forward and aft-segments of propellant charge are bonded to the gas barrier and assembly of the telescoped round is completed. Results of the firing of round l-6 is shown in table I. The position of the gas barrier in the assembled round in relation to the rotating ban of the projectile is the same as described in FIG. 1.

sistance to flow of gas through a given barrier material, the smaller the amount of barrier material required. The upper limit as to the thickness of a flame barrier is dependent on its consumability under a given set of firing conditions.

It is clear that numerous materials can be employed as a gas barrier in the propellant charge of this invention. Particularly, suitable materials will have a fast-buming rate and include cellulose nitrate plastics, acrylic polymers and polystyrenes including styrofoam. Gas barriers prepared from single and double base propellants prepared by any of the well known propellant manufacturing processes such as casting or extru sion in which consolidated nonporous propellant is produced can be employed very efiectively.

Illustrative of other materials which can be employed as the gas barrier in this invention include the epoxy resins. Particularly suitable epoxy resins are the reaction products of epichlorohydrin and 2,2-bis(p-hydroxyphenyl)propane generally referred to as Bisphenol A. Epoxy resins of this type are available commercially as Epon, Araldite or Epi-Rez resins. Epoxy resins can be cured to form gas barriers with any of the well-known epoxy curing agents including phenol ethers such as mono, or di-methylol phenol; amines, such as ethylene diamine and diethylenetriamine; polyamides prepared by condensation of a dimeric fatty acid with a polyamine such as ethylene diamine and the like. Gas barriers prepared from epoxy resins, in general, have a slow burning rate. Gas barriers prepared from these materials are employed as a very thin nonporous film which will temporarily resist flow of gas. Rounds of caseless ammunition employing such barriers will leave little or no traces of residue in the chamber and barrel of the forearm after a firing. The gas barriers of this invention must, as a minimum, provide abarrier having at least the same TABLE I Velocity Maximum chamber Propellant 36 feet pressure (p.s.l.)

charge Projectile from gun weight weight muzzle, 'Irans- Impetus 1 Energy E (grams) (grams) feet/sec. ducer Crusher ft.-lbs./lb. factor 1 2 1 Control 48. 97 98. 75 3, 230 52,100 319, 750 91, 2 Control (non- 49. 29 99. 16 3, 557 55, 000 46, 100 386, 813 110. 5

telescoped),

-. Telescoped 49.16 99. 00 3, 680 70, 000 60, 400 392, 170 112.0 49. 36 99. 57 3, 498 68, 100 375, 198 107. 2 49. 11 98. 47 3, 564 70, 000 56, 300 387, 015 110. 6 49. 26 98. 47 3, 564 68, 000 55, 100 388, 089 110. 9

1 Calculated value. {Energyjactor is delivered impetus expressed as percent of theoretical (350, 000 it. lbs./lb.).

As can be seen from table I, velocity of the projectile of example l, the control round in which no gas barrier is employed, is about 300 feet per second slower that the velocity of the projectiles from each of rounds 3-6 in which a gas barrier was employed. Projectile velocity and the efficiency factor of round 2 in which the projectile is seated (nontelescoped) and rounds 3-6 (telescoped) is similar. Theballistic efficiency of telescoped caseless rounds in which a gas barrier is employed is improved over the round fired without a gas barrier and is substantially the same as the round fired in a nontelescoped form.

Gas barriers which can be employed with telescoped caseless ammunition to increase ballistic efirciency must be consumable and nonporous. By the term consumable" as used herein, is meant, that the gas barrier material is either combustible or the material through a combination of heat, pressure and sweep of exhaust gases will leave the chamber and barrel of the firearm substantially free of residue after a firing; By the term "nonporous" as used herein, is meant, that the material will at least momentarily resist movement of gas therethrough upon application of a pressure differential across it. The gas barrier material must also be compatible with the propellant composition comprising the molded propellant charge.

The amount or thickness of the gas barrier employed in a telescoped round depends principally on the porosity of the material employed and its consumability. The greater the recross-sectional area as a cross section of the aft-surface forward-end of the propellant charge.

What I claim and desire to protect by Letters Patent is:

1. In a telescoped round of caseless ammunition comprising a propellant charge having an axial cavity, a projectile completely housed within said axial cavity and a primer, the improvement comprising a propellant charge having a gas barrier secured therein, said gas barrier separating the propellant charge into a forward-end and an aft-end, said gas barrier having at least the same cross-sectional area as the cross-sectional area of the aft-surface of the forward-end of the propellant charge.

2. The telescoped round of claim 1 wherein the gas barrier is prepared from single base propellant.

3. The telescoped round of claim 1 wherein the gas barrier is prepared from double base propellant.

4. The telescoped round of claim 1 wherein the gas barrier is prepared from styrofoam.

5. The telescoped round of claim I wherein the gas barrier is prepared from an epoxy resin.

6. The telescoped round of caseless ammunition of claim 1 wherein the gas barrier is positioned within the propellant charge so that the forward-surface of the gas barrier is in line with or aft of the contacting surface of the projectile, said contacting surface being the surface of the projectile making initial contact with the rifling in the barrel of the gun in which the telescoped round is fired.

barrier is secured to the outside surface of the forward-end of the propellant charge.

10. The telescoped round of claim 9 wherein additional gas barrier is secured to the surface area defined by the axial cavity in the forward-end of the propellant charge.

11. The telescoped round of claim 10 wherein the gas barrier is prepared from an epoxy resin.

# i i i 

1. In a telescoped round of caseless ammunition comprising a propellant charge having an axial cavity, a projectile completely housed within said axial cavity and a primer, the improvement comprising a propellant charge having a gas barrier secured therein, said gas barrier separating the propellant charge into a forward-end and an aft-end, said gas barrier having at least the same cross-sectional area as the cross-sectional area of the aftsurface of the forward-end of the propellant charge.
 2. The telescoped round of claim 1 wherein the gas barrier is prepared from single base propellant.
 3. The telescoped round of claim 1 wherein the gas barrier is prepared from double base propellant.
 4. The telescoped round of claim 1 wherein the gas barrier is prepared from styrofoam.
 5. The telescoped round of claim 1 wherein the gas barrier is prepared from an epoxy resin.
 6. The telescoped round of caseless amMunition of claim 1 wherein the gas barrier is positioned within the propellant charge so that the forward-surface of the gas barrier is in line with or aft of the contacting surface of the projectile, said contacting surface being the surface of the projectile making initial contact with the rifling in the barrel of the gun in which the telescoped round is fired.
 7. The telescoped round of claim 6 wherein the projectile has a rotating band having a forward surface, and the forward-surface of the rotating band is the contacting surface of the projectile.
 8. The telescoped round of claim 6 wherein the projectile has a guilding metal jacket and the forward-end of the projectile has an ogive, the base of the ogive comprising the contacting surface of the projectile.
 9. The telescoped round of claim 6 wherein additional gas barrier is secured to the outside surface of the forward-end of the propellant charge.
 10. The telescoped round of claim 9 wherein additional gas barrier is secured to the surface area defined by the axial cavity in the forward-end of the propellant charge.
 11. The telescoped round of claim 10 wherein the gas barrier is prepared from an epoxy resin. 